520ST problem with the floppy drive

[tjlazer]

I am refurbing some 520 ST's and I have one with a problem. It will not read a disk and half the time it boots up with no drives showing on TOS desktop. It's definitely not the floppy drives as I am using them no problem on other ST's. I tried swapping all chips and I figured it was the WD1772 chip so I got some replacements and it's still doing it. Any ideas on where I can start looking at? I swapped out the TOS with a new set and that also did not help.

[oky2000]

I am refurbing some 520 ST's and I have one with a problem. It will not read a disk and half the time it boots up with no drives showing on TOS desktop. It's definitely not the floppy drives as I am using them no problem on other ST's. I tried swapping all chips and I figured it was the WD1772 chip so I got some replacements and it's still doing it. Any ideas on where I can start looking at? I swapped out the TOS with a new set and that also did not help.

 

I take it you mean ST as in original ST/STm without built in drive? I had this problem on my STM with either the machine sometimes not booting or reading disks but more often than not the desktop would take forever to boot as if you had no disk in the drive, and then it would have no drive icons on the GEM desktop etc.

 

If you do, this is the loose TOS ROM problem that was the bane of my life in 1986. So remove the TOS chips, check all contacts and clean ROM and sockets and then reseat all the ROMs and retry. Good luck